The boiling up of a metastable liquid when the vaporization fronts appear is considered by theoretically and experimentally. Boiling up occurs as usually on a surface of a heater. At the first stage the growth of a spherical vapor bubble is observed. If the temperature of liquid exceeds threshold value, the vaporization fronts develop near to line of contact of a vapor bubble and heater. Fronts of vaporization extend along a heater with constant speed. It is direct transition from one-phase convection to a film boiling. Such scenario of crisis of a convective heat transfer also is possible in the nuclear reactor equipment. The model of steady propagation of the vaporization front is developed. The temperature and velocity of propagation of the interface are determined from the balance equations for the mass, momentum, and energy in the neighborhood of the vaporization front and the condition of stability of motion of the interface. It is shown that a solution of these equations exists only if the liquid is heated above a threshold value. The velocity of propagation of vaporization front has threshold value also. The calculated velocity of interface motion and the threshold value of temperature are in reasonable agreement with available experimental data for various liquids within wide ranges of saturation pressures and temperatures of the overheated liquid.

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